Towards a realistic microscopic description of highway traffic

Simple cellular automata models are able to reproduce the basic properties of highway traffic. The comparison with empirical data for microscopic quantities requires a more detailed description of the elementary dynamics. Based on existing cellular automata models we propose an improved discrete model incorporating anticipation effects, reduced acceleration capabilities and an enhanced interaction horizon for braking. The modified model is able to reproduce the three phases (free-flow, synchronized, and stop-and-go) observed in real traffic. Furthermore we find a good agreement with detailed empirical single-vehicle data in all phases.Comment: 7 pages, 7 figure

An empirical test for cellular automaton models of traffic flow

Based on a detailed microscopic test scenario motivated by recent empirical studies of single-vehicle data, several cellular automaton models for traffic flow are compared. We find three levels of agreement with the empirical data: 1) models that do not reproduce even qualitatively the most important empirical observations, 2) models that are on a macroscopic level in reasonable agreement with the empirics, and 3) models that reproduce the empirical data on a microscopic level as well. Our results are not only relevant for applications, but also shed new light on the relevant interactions in traffic flow.Comment: 28 pages, 36 figures, accepted for publication in PR

Variations in killer-cell immunoglobulin-like receptor and human leukocyte antigen genes and immunity to malaria

Malaria is one of the deadliest infectious diseases in the world. Immune responses to Plasmodium falciparum malaria vary among individuals and between populations. Human genetic variation in immune system genes is likely to play a role in this heterogeneity. Natural killer (NK) cells produce inflammatory cytokines in response to malaria infection, kill intraerythrocytic Plasmodium falciparum parasites by cytolysis, and participate in the initiation and development of adaptive immune responses to plasmodial infection. These functions are modulated by interactions between killer-cell immunoglobulin-like receptors (KIR) and human leukocyte antigens (HLA). Therefore, variations in KIR and HLA genes can have a direct impact on NK cell functions. Understanding the role of KIR and HLA in immunity to malaria can help to better characterize antimalarial immune responses. In this review, we summarize the different KIR and HLA so far associated with immunity to malaria.This work was supported through the DELTAS Africa Initiative (Grant no. 107743), that funded Stephen Tukwasibwe through PhD fellowship award, and Annettee Nakimuli through group leader award. The DELTAS Africa Initiative is an independent funding scheme of the African Academy of Science (AAS), Alliance for Accelerating Excellence in Science in Africa (AESA) and supported by the New Partnership for Africa’s Development Planning and Coordinating Agency (NEPAD Agency) with funding from the Wellcome Trust (Grant no. 107743) and the UK government. Francesco Colucci is funded by Wellcome Trust grant 200841/Z/16/Z. The project received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 695551) for James Traherne and John Trowsdale. Jyothi Jayaraman is a recipient of fellowship from the Centre for Trophoblast Research

Ein stochastisches Werkstoffmodell zur Beschreibung von Kriechen und zyklischem Verhalten metallischer Werkstoffe

The starting-point of this dissertation was the stochastic model of STECK which simulates the essential mechanisms of monotonic inelastic deformations on a stochastic basis. In order to describe cyclic material behaviour, the stochastic model has been extended by the simulation of internal back stresses. This extension is based on the widely accepted concept that at inelastic deformation the dislocation gliding processes are driven by the effective stress which results from the difference between the applied stress and the internal back stress. The evolution of back stresses has been added to the model by introducing additional transition probabilities which consider the influence of the effective stress on the deformation process. The extended stochastic model in mean-value formulation has been fitted to three different materials. Besides an extensive fitting to creep-tests of pure aluminium, simultaneous parameter-fittings to monotonic and cyclic tension-tests of the austenitic steels AISI 316 L and AISI 304 have been carried out. The results of the model-fittings and model-predictions confirm that the developed model is able describe in an averaged form material mechanisms which are important for the cyclic behaviour in the high temperature regime. (orig.)SIGLEAvailable from TIB Hannover: RR 5346(5) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDeutsche Forschungsgemeinschaft (DFG), Bonn (Germany)DEGerman

Untersuchungen an einer Axialgleitringdichtung fuer den Einsatz in Dampfturbinen Abschlussbericht

In order to achieve a higher efficiency of industrial steam turbines (up to 50 MW) a new sealing system (mechanical face seal) was examined. As the operating performance of these seals under the interesting conditions has not been explored yet, a test rig for the examination of hot steam seals (d_s=305 mm, #nu#_m_a_x#approx#200 m/s, p_m_a_x#approx#80 bar and T_m_a_x#approx#550 C) was designed. For the further development of secondary seals a test rig was constructed that simulates the tribilogical load collective of secondary seals. Finally, in order to improve seal calculation the at the research center existing calculation program AGRD was extended by pressure- and temperature-dependent medium data, the energy equalion and distortions. The measurements of the mechanical face seal show the expected and calculated behaviour for the power cross and the seal leakage. The seal proved its operation safety in several tests, including a 24h-run. Under strongly instationary operation conditions both test seals failed. At the moment the seal has no sufficient operation safety for a long-term application in a power station, but the analysis of failure leads to the conclusion that the technical problems can be solved. (orig.)Um bei Industriedampfturbinen (bis etwa 50 MW) einen hoeheren Wirkungsgrad zu erreichen, sollte fuer den Ausgleichskolben ein neues Dichtungssystem (Axialgleitringdichtung) untersucht werden. Da das Betriebsverhalten derartiger Dichtungen in dem hier interessierenden Parameterbereich noch nicht erforscht ist, wurde ein Pruefstand entwickelt und aufgebaut, an dem derartige Heissdampf-Dichtungen (mit d_s=305 mm, #nu#_m_a_x#approx#200 m/s, p_m_a_x#approx#80 bar und T_m_a_x#approx#550 C) betrieben werden koennen. Ausserdem war fuer die Weiterentwicklung der Sekundaerdichtungen ein Pruefstand zu konstruieren, mit dem sich das in der Praxis vorhandene tribologische Beanspruchungskollektiv simulieren laesst. Schliesslich wurde zur genaueren Nachrechnung der Dichtung das an der Forschungsstelle vorhandene Dichtungsprogramm AGRD und die druck- und temperaturabhaengigen Stoffdaten, die Energiegleichung und die Verformungsberechnung erweitert. Die Messungen an der Axialgleitringdichtung zeigten den fuer den Verlustleistung und den Leckagenmassenstrom erwarteten und berechneten Verlauf. Die Dichtung hat ihre Funktionssicherheit in mehreren Versuchen, darunter ein 24 h-Versuch, bewiesen. Bei stark instationaerem Betrieb traten an beiden Versuchsichtungen Schaeden auf. Zur Zeit besitzt die Dichtung noch keine ausreichende Betriebssicherheit fuer einen Langzeiteinsatz im Kraftwerk, jedoch laesst die Analyse des Befundes darauf schliessen, dass die technischen Probleme loesbar sind. (orig.)SIGLEAvailable from TIB Hannover: F98B1860+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Grundlagen fuer die Weiterentwicklung von Axialfederlagern und -gleitringdichtungen mit aerodynamischer Schmierung Abschlussbericht

Aerodynamic axial bearings and sliding ring seals are especially suitable for extreme operating conditions. Compared with conventional bearings or the previously used labyrinth seals they lead to appreciable improvements in efficiency. To make their further development for higher circumferential speeds, loads and pressures possible, the basis of design is considerably expanded in this work. In the new bearing programme, in addition to the turbulence, centrifugal force and deformation effect, as well as the pressure build-up, are taken into account by an aerostatic starting aid. With this, the parameters of the most important aerodynamic axial bearing shapes can be precalculated and optimised safely, even for difficult operating conditions. The reliability of the basis of calculations is proved in extensive measurements, the load limit of different pairs of materials or surface layers is determined, the effect of fine surface structure is analysed and the resistance to wear of selected variants is proved. In the sealing calculation expanded to high pv values, the turbulence and deformation effect are to the fore, where the sealing ring deformation is determined by coupling the sealing programme with the finite element program ANSYS. Extensive measurements on three different experimental seals confirm the reliability of the calculated parameters and the high working safety of this type of sealAerodynamische Axiallager und -gleitringdichtungen sind fuer extreme Betriebsbedingungen besonders geeignet. Sie fuehren gegenueber konventionellen Lagern bzw. den bisher gebraeuchlichen Labyrinthdichtungen zu wesentlichen Wirkungsgradverbesserungen. Um deren Weiterentwicklung zu hoeheren Umfangsgeschwindigkeiten, Belastungen und Druecken zu ermoeglichen, werden in dieser Arbeit die Auslegungsgrundlagen wesentlich erweitert. Im neuen Lagerprogramm werden zusaetzlich der Turbulenz-, Fliehkraft- und Verformungseinfluss sowie der Druckaufbau durch eine aerostatische Anfahrhilfe beruecksichtigt. Damit lassen sich nun die Kennwerte der wichtigsten aerodynamischen Axiallager-Bauformen auch fuer schwierige Betriebsbedingungen sicher vorausberechnen und optimieren. In umfangreichen Messungen wird die Zuverlaessigkeit der Berechnungsgrundlagen nachgewiesen, die Belastungsgrenzen verschiedener Werkstoffpaarungen bzw. Oberflaechenschichten ermittelt, der Einfluss der Oberflaechenfeinstruktur analysiert und die Verschleissfestigkeit ausgesuchter Varianten nachgewiesen. Bei der auf hohe p x v-Werte erweiterten Dichtungsberechnung stehen der Turbulenz- und der Verformungseinfluss im Vordergrund, wobei die Dichtring-Verformungen ueber eine Kopplung des Dichtungsprogrammes mit dem FE-Programm ANSYS ermittelt werden. Umfangreiche Messungen an drei verschiedenen Versuchsdichtungen bestaetigen die Zuverlaessigkeit der berechneten Kennwerte und die hohe Betriebssicherheit dieser Dichtungsbauart. (orig.)Available from TIB Hannover: RA 1581(556) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Wirtschaft, Bonn (Germany); Arbeitsgemeinschaft Industrieller Forschungsvereinigungen e.V., Koeln (Germany)DEGerman

Einfluss der Dissipationsenergie auf das Betriebsverhalten aerodynamischer Gleitringdichtungen bei hohen Umfangsgeschwindigkeiten und hohen Druecken Abschlussbericht

SIGLEAvailable from TIB Hannover: RA 1581(667) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Wirtschaft, Bonn (Germany); Arbeitsgemeinschaft Industrieller Forschungsvereinigungen 'Otto von Guericke' e.V. (AIF), Koeln (Germany)DEGerman